1. Field of the Invention
The present invention relates to an improved method of polishing the end face of a ferrule as one member constituting the optical connector into a convex spherical surface.
2. Description of the Related Art
It is a common practice that an optical fiber for transmitting optical signals, which is composed of a core of quartz or the like and a clad covering it, has its end held by a ferrule, and the end face of the ferrule is polished into a convex spherical surface, with its vertex being at the core, such that the resulting surface is mirror-finished or rough-finished.
The conventional method of polishing the end face of a ferrule into a convex spherical surface consists of pressing the end face of the ferrule holding an optical fiber against a polishing sheet, which is formed of a resin substrate and diamond abrasive grains bonded thereto by a binder and is fixed on an elastically deformable base of the polishing machine, while moving the base such that the ferrule sweeps a nearly constant path on the polishing sheet which is being supplied with water.
However, the disadvantage of the conventional method resides in that in the layer of abrasive grains of the polishing sheet, which is composed of a sheet and diamond abrasive grains attached thereto, has a short life, with the abrasive grains being deformed and deteriorated and dropped off, after several repetitions of the polishing operation.
Another disadvantage resides in that the end face of the ferrule polished by using a fresh polishing sheet is rougher than the end face of the ferrule polished by using a worn-out polishing sheet. This is undesirable although the difference in surface roughness is within tolerance. Thus, there is a demand for improvement in the constancy of surface roughness.
Moreover, carrying out polishing by moving the base of the polishing machine, to which the polishing sheet is fixed, such that the ferrule holding an optical fiber sweeps a nearly constant path on the polishing sheet is not economical because the polishing sheet remains partly unused (or the polishing sheet has a part with which the end face of the ferrule does not come into contact). In addition, simultaneous polishing of the optical fiber and the ferrule which differ in hardness necessitates the use of a polishing sheet with expensive diamond abrasive grains. This and the foregoing prevent the cost reduction of the product.